According to $MO$ theory,which of the following lists ranks the nitrogen species in terms of increasing bond order?

When two atomic orbitals combine,they form:

The bond order in $O_2^{2-}$ is

According to molecular orbital theory,the total number of bonding electron pairs in $O_2$ is

Consider the following statements.
$I$. In the conversion of $O_2$ to $O_2^{2+}$,bond order decreases.
$II$. In the conversion of $O_2$ to $O_2^{2+}$,magnetic property is not changed.
$III$. In the conversion of $O_2$ to $O_2^{2+}$,bond length decreases.
$IV$. $O_2^{2-}$ and $B_2$ have same bond order.
Identify the correct statements.

The bond lengths of $C_2$,$N_2$ and $B_2$ molecules are $X_1$,$X_2$ and $X_3$ $pm$ respectively. The correct order of their bond lengths is